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Health
Problems Aids
What is AIDS?
AIDS stands for acquired
immunodeficiency syndrome. An HIV-infected person receives a diagnosis of
AIDS after developing one of the CDC-defined AIDS indicator illnesses. An
HIV-positive person who has not had any serious illnesses also can receive
an AIDS diagnosis on the basis of certain blood tests (CD4+ counts).
A positive HIV test result does not mean
that a person has AIDS. A diagnosis of AIDS is made by a physician using
certain clinical criteria (e.g. AIDS indicator illnesses). Infection with
HIV can weaken the immune system to the point that it has difficulty
fighting off certain infections. These types of infections are known as
"opportunistic" infections because they take the opportunity a
weakened immune system gives to cause illness.
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What causes
AIDS?
Many of the infections that cause problems or may be life-threatening for
people with AIDS are usually controlled by a healthy immune system. The
immune system of a person with AIDS is weakened to the point that medical
intervention may be necessary to prevent or treat serious illness.
Today there are medical treatments that can
slow down the rate at which HIV weakens the immune system. There are other
treatments that can prevent or cure some of the illnesses associated with
AIDS. As with other diseases, early detection offers more options for
treatment and preventative care.
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What is the evidence
that HIV causes AIDS?
Although the scientific evidence is overwhelming and compelling
that HIV is the cause of AIDS, the disease process is not yet completely
understood.
This incomplete understanding has led some
to make statements that AIDS is not caused by an infectious agent. This is
not only misleading, but may have dangerous consequences. Before the
discovery of HIV, evidence from epidemiologic studies involving tracing of
patients' sex partners and cases occurring in blood recipients had clearly
indicated that the underlying cause of the condition was an infectious
agent. Infection with HIV has been the sole common factor shared by AIDS
cases throughout the world among homosexual men, transfusion recipients,
persons with hemophilia, sex partners of infected persons, children born
to infected women, and occupationally exposed health care workers.
Recommendations to prevent HIV and AIDS involve guidance to avoid or
modify behaviors that pose a risk of transmitting the virus as well as the
use of the HIV antibody test to screen donors of blood and organs.
Although HIV is the underlying cause of
AIDS, much remains to be known about exactly how HIV causes immune
deficiency. However, this incomplete understanding does not indicate that
the virus is harmless. Why some persons exposed to HIV will become
infected while others do not is also not known, but this is likely related
to the amount of virus in the exposure and the route of entry (e.g., more
than 90% of persons transfused with an HIV-infected unit of blood become
infected).
Approximately half of HIV-infected adults
will develop AIDS within 8 to 10 years of infection with HIV, while others
continue to progress to AIDS after that period. As with any disease with a
long latency period, it is possible that co-factors play a role in disease
development. However, extensive epidemiologic and laboratory studies of
HIV-infected persons have failed to identify any consistent factor,
including drug use, malnutrition, or co-infections with other organisms,
that affects the rate of progression to AIDS.
Clearly, more research is needed on the
factors that contribute to HIV infection and the development of AIDS.
However, the inescapable conclusions of more than 10 years of
epidemiologic and virologic research are that most people, if exposed
through sexual contact or injecting drug use, are susceptible to HIV
infection, and if they become infected, most, if not all, persons will
develop AIDS.
Below are citations to several articles by
researchers at the CDC as well as by others which contain more information
regarding HIV infection as the cause of AIDS.
- Cohen J. The Duesberg phenomenon.
Science 1994 Dec;266(9):1642-44.
- Cohen J. Fulfilling Koch's postulates.
Science 1994 Dec;266(9):1647.
- Cohen J. Could drugs, rather than a
virus, be the cause of AIDS? Science 1994 Dec;266(9):1648-49.
- Blattner W, Gallo RC et al. HIV causes
AIDS. Science 1988;241:515-16.
- Duesberg P. HIV is not the cause of
AIDS. Science 1988;241:514-17.
- Weiss R. How does HIV cause AIDS?
Science May 1993;260:1273-79.
- Winkelstein W, Wiley J, Padian N, et al.
The San Francisco men's health study: continued decline in HIV
seroconversion rates among homosexual/bisexual men. Am J Public Health
1988;78:1472-74.
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How long does it
take for HIV to Causes AIDS?
Since 1992, scientists have estimated that about half the people
with HIV develop AIDS within 10 years after becoming infected. This time
varies greatly from person to person and can depend on many factors,
including a person's health status and their health-related behaviours.
Today there are medical treatments that can
slow down the rate at which HIV weakens the immune system. There are other
treatments that can prevent or cure some of the illnesses associated with
AIDS, though the treatments do not cure AIDS itself. As with other
diseases, early detection offers more options for treatment and
preventative health care.
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What is meant by "Asymptomatic
Period"?
It is possible to be infected with HIV without showing
symptoms of illness. An individual can transmit the virus to others, even
if he or she shows no symptoms. In the United States, an estimated 650,000
to 900,000 persons currently are infected with HIV.
Many people do not develop any symptoms
when they first become infected with HIV. Some people, however, have a
flu-like illness within a month or two after exposure to the virus. They
may have fever, headache, malaise, and enlarged lymph nodes (organs of the
immune system) easily felt in the neck and groin. These symptoms usually
disappear within a week to a month and are often mistaken for those of
another viral infection.
More persistent or severe symptoms may not
surface for a decade or more after HIV first enters the body in adults,
and within two years in children born with HIV infection. This period of
"asymptomatic" infection is variable, however. Some people may
begin to have symptoms in as soon as a few months, whereas others may be
symptom-free for more than 10 years. During the asymptomatic period,
however, HIV is actively infecting and killing cells of the immune system.
HIV's effect is seen most obviously in the blood levels of CD4+ T cells
(also called T4 cells) -- the immune system's key infection fighters. The
virus initially disables or destroys these cells without causing symptoms.
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What is meant by "Window
Period"?
Many people express concern regarding the length of time
following infection for an individual to develop detectable antibodies to
HIV. This is known as the "Window Period". According to the CDC,
most persons infected with HIV develop antibodies against the virus within
three months after the infection. This time period for antibody
development is based on the results of numerous studies of persons with
hemophilia, persons who received transfusions from HIV-infected
individuals, and spouses of both these groups; homosexual men; and
occupationally exposed health-care workers. The CDC studies indicate that
it is highly unlikely that HIV infection would go unrecognized for
prolonged periods (over six months) in persons who are infected.
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What is the primary impact of HIV on the
immune system?
In a healthy person, the normal range of certain white
blood cells called T4 lymphocyte cells (helper cells) is usually between
600 and 1200 (T4) cells per cubic millimeter (cells/mm3). (The range
depends on the test used.) When human immunodeficiency virus (HIV) enters
the bloodstream, it primarily infects T4 cells. Asymptomatic individuals
infected with HIV usually have a lower than normal T4 cell count, and
people with AIDS generally have between 0 and 500 T4 cells/mm3. The number
of T8 lymphocyte cells (suppressor cells) in an HIV-infected person
usually stays about the same. Because the number of T4 cells is low, the
total T-cell count is lower than normal, and the T4/T8 cell ratio is lower
than the usual 2 to 1 ratio.
HIV infection not only reduces the number
of T4 cells, it can also impair a T4 cell's functioning. HIV-infected
individuals with very low T4 cell counts tend to have more serious
infections. Therefore, regular immunologic tests to determine T4, T8, and
total T-cell counts can be an important element in monitoring the health
of an HIV-infected person.
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This page was last updated on 04 December 2006 17:20:28
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